This invention relates to data communications networks using coaxial cable and connectors, in particular to a network with self-terminating coaxial tap connectors.
FIG. 1 illustrates a known type of data communications network using coaxial cable and connectors. Coaxial cable segments 22 form a backbone which is tapped to connect to computers or peripheral stations 20. Connections are made by coupling cable connectors 26 to matching device connectors 29. Cable connectors 26 can be male BNC style plugs, while matching device connectors 29 can be female BNC style sockets. Each end of a cable segment 22 has a cable connector 26. FIG. 1A shows an exploded view of the connections to a T connector 28. A T connector 28 has two oppositely mounted device connectors 29 and an orthogonally mounted cable connector 26. The T connector's two device connectors 29 receive cable connectors 26 from two cable segments 22. The T connector's cable connector 26 connects to a device connector 29 on a transceiver 30. The transceiver 30 has a drop cable 32 connecting via a station connector 36 to a station 20. The specifications for a network of this type can be found in ANSI/IEEE Standard 802.3a, Medium Attachment Unit and Baseband Medium Specifications, Type 10BASE2 (Section 10), Institute of Electrical and Electronics Engineers, Inc., New York, 1987.
Other cable, tap, and connector configurations are possible. For example, the T connector 28 could be replaced with two device connectors 29 mounted on the case of transceiver 30. Then, two separate cable segments 22 with cable connectors 26 would each connect to a device connector 29 on transceiver 30. In this case, the tap or T connection would be formed internal within transceiver 30. Another alternative is to mount the electronics of transceiver 30 within the case of a station 20 and have two device connectors 29 mounted on the case of station 20. Again, the tap or T connection would be formed within station 20. Another alternative is to mount the electronics of transceiver 30 within the case of a station 20, but have a single device connector 29 mounted on the case of station 20, and use a T connector 28 to connect two cable segments 22 to the single device connector 29. In general, these coaxial networks will include cable connectors 26 coupling to device connectors 29 at numerous points in the network.
These cable configurations have a common problem. Connections to coaxial cable 22 must be carefully controlled to prevent disturbances in its characteristic impedance, which can cause signal loss and reflections which interrupt operation of the network. It is necessary to terminate any open connector such as an uncoupled cable connector 26, or an uncoupled device connector 29 on a T connector 28. This can be done with a terminator 34 which is matched to the characteristic impedance of coaxial cable 22. Should a cable end be uncoupled, dividing the network into two sections, neither section will function properly since each section has an open end which is not terminated. It is an object of this invention to form a network in which uncoupled connectors are automatically self-terminated, thereby allowing the separated network sections to remain operational.
It is also important when forming tap connections, such as by T connectors 28, or by wiring internal to a transceiver 30 or station 20, to minimize the length of the tap connection, that is the distance from the commonly connected coaxial cable connectors 26 to the termination of the tap at a transceiver 30. It is a further object of this invention to provide a tap connector which can be mounted on a printed circuit board, for minimizing the length of the tap, and reducing the disturbance to an attached coaxial cable network.